Expand.
Answer: $\begin{aligned} &\phantom{=}({x^2+4})(x^2-6) \\\\ &={x^2}(x^2-6){+4}(x^2-6) \end{aligned}$ $\begin{aligned} &=x^4-6x^2+4x^2-24 \\\\ &=x^4-2x^2-24 \end{aligned}$